More specifically, the present invention relates to an infusion method and device for making a “weak” coffee beverage or so-called “American coffee” using a sealed capsule containing a measure of ground coffee.
For percolating coffee, a coffee percolator is used comprising a pressurized-hot-water dispenser, and a cup facing the dispenser and housing a rigid sealed capsule containing a measure of ground coffee. The sealed capsule is normally defined by a cup-shaped body of thermoplastic material closed at one end by an end wall, and at the other end by a sealing wall normally made of metal sealing foil; and the cup is movable, with respect to the dispenser, to and from an infusion position connected to the dispenser, and houses the sealed capsule with the sealing wall facing the dispenser.
In known coffee percolators employing a sealed capsule, the hot water, emitted by the dispenser at a pressure of normally around 8-10 atmospheres, normally flows into the sealed capsule by at least one feed needle piercing the sealing wall when the cup is moved into said infusion position. Once inside the sealed capsule, the hot water mixes with and compresses the ground coffee towards the end wall, which, by virtue of the internal pressure and temperature, deforms outwards into contact with a number of hollow extraction needles carried by the cup and each having a number of longitudinal lateral slits of about 0.2 mm in width. The hollow extraction needles gradually penetrate the sealed capsule to a length normally equal at most to a fifth of the depth of the sealed capsule, and allow the coffee beverage to flow out through a percolator spout communicating with the inside of the cup.
Known percolators of the type described above are normally so-called “espresso” percolators, in which the content of a sealed capsule is used to produce an “espresso coffee”, i.e. a coffee beverage of about 20 cm3 in volume and topped with an air-emulsified layer. Such a layer, which is extremely popular with consumers and invariably sought after by manufacturers, is formed by the small flow section and the length of the extraction needle slits, which, being much narrower than the coffee grains, induce steady vortices of emulsion at the outlet, which are further created by the high hot-water feed pressure, by compression of the ground coffee against the end wall of the sealed capsule (normally enhanced by a press effect produced by the sealed capsules normally being conical), and by the short length of the extraction needles, which intercept the beverage close to the end wall of the sealed capsule.
Known percolators of the above type, however, fail to provide, using the same sealed capsule, for producing a “weak” beverage, i.e. “American coffee”, of about 200 cm3 in volume. This is because, after a relatively short time, gradual compaction of the ground coffee against the end wall of the sealed capsule reduces hot-water flow through the sealed capsule to such an extent as to make the time taken to produce such a “weak” beverage unacceptable. Moreover, preferential passages are soon formed in the ground coffee inside the sealed capsule, so that, within a relatively short initial period, a beverage closely resembling espresso coffee, with, in this case, an undesired emulsified surface layer, is produced, followed by production of no more than barely coloured hot water, the resulting mixture of which is normally considered undrinkable.